US4605370A - Method and apparatus for burning away organic components in raw phosphate - Google Patents

Method and apparatus for burning away organic components in raw phosphate Download PDF

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Publication number
US4605370A
US4605370A US06/652,329 US65232984A US4605370A US 4605370 A US4605370 A US 4605370A US 65232984 A US65232984 A US 65232984A US 4605370 A US4605370 A US 4605370A
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reactor
stage
gas
suspension
organic components
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English (en)
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Soren Hundebol
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FL SMIDTH & Co 77 VIGERSLEV DK-2500 VALBY COPENHAGEN DENMARK A DANISH Co AS
FLSmidth and Co AS
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FLSmidth and Co AS
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Assigned to F.L. SMIDTH & CO. A/S., 77 VIGERSLEV, DK-2500 VALBY, COPENHAGEN, DENMARK, A DANISH COMPANY reassignment F.L. SMIDTH & CO. A/S., 77 VIGERSLEV, DK-2500 VALBY, COPENHAGEN, DENMARK, A DANISH COMPANY ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: HUNDEBOL, SOREN
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/01—Treating phosphate ores or other raw phosphate materials to obtain phosphorus or phosphorus compounds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

Definitions

  • the invention relates to a method and an apparatus for calcining raw phosphate, i.e. burning away organic components and expulsion of CO 2 by burning in suspension, being particularly suited for treating raw phosphate containing organic components in an amount which may prevent it from being used directly, e.g. for the production of phosphoric acid according to the wet process.
  • Such known methods may involve calcining in fluid-bed reactors where the calcining takes place in two stages in fluid-bed reactors, see e.g. U.S. Pat. No. 3,995,987, or calcining in one stage in a suspension transport reactor, see, e.g. FR No. 2486924.
  • a method of burning away organic components in phosphate raw material is characterized in that the burning takes place in two stages each having its separate air supply, in which the raw material in the first stage is suspended in and entrained by a first air/gas stream having a velocity of 2-10 m/sec.
  • first suspension having a density of 1-50 kg/m 3 , to which fuel, if desired, is supplied, so that the majority of the organic components are burnt
  • the material treated in the first stage subsequently being separated from the gas stream and passed to the second stage and suspended in a second air/gas stream having a velocity of 0.05-15 m/sec to form a second suspension haing a density of 75-1600 kg/m 3 , to which fuel, if desired, is supplied, whereafter the material treated in the second stage is discharged as a product; in that the ratio between the amount of air introduced into the first stage and the amount passed to the second stage is higher than 2, preferably 3; in that the material retention time in the second stage is at least 4, preferably 10, time as large as the material retention time in the first stage; and in that the weight ratio raw material/air supplied to the first stage is within the range 1-4, while the corresponding ratio for the second stage is within the ratio 2-30, preferably 3-20.
  • the raw material used for the method according to the invention is particulate raw phosphate, preferably with a maximum average size of 3 mm, in particular with a degree of fineness of 1-0.05, where a particulate material is said to have the degree of fineness x when it yields 50 weight % sieve residue on an x mm mesh sieve.
  • the mew method is characterized in that the reaction temperature lies within the range 700°-850° C. in each of the two stages, and that the first stage operates with an oxygen percentage in the exit gas of 0-4 and with a smaller air surplus than the second stage in which the oxygen percentage in the exit gas is at least twice the percentage in the first stage.
  • the exit gas flow from each of the two stages may be used for drying and preheating the raw material supplied to the plant prior to the material being passed to the first reactor stage.
  • the invention also includes apparatus for carrying out the new method, the apparatus comprising two series-coupled reactors provided with ducts for supplying fuel, combustion air and preheated material to the reactors, of which the first reactor is a suspension transport reactor for carrying out the first stage, and the second reactor is a suspension reactor for carrying out the second stage; a material separator for separating the product treated in the first reactor; a cooler coupled to the second reactor for cooling the treated material; and a pipe for removing the material treated in the second reactor.
  • first stage reactor may particularly be used calciners of the type formed as a tube-shaped reactor with vertical shaft and conical bottom, which at the bottom is equipped with pipes for supplying fuel and preheated material and an axially arranged air supply pipe, and which at its top is provided with a pipe for transferring the suspension to the material separator.
  • Second stage reactor may particularly be used fluid-bed and spouted-bed reactors.
  • the plant has first and second reactors 3,5, which are series-coupled.
  • the first reactor 3 is a suspension transport or "flash"-calciner with short material retention time with supplies of combustion air, raw material and fuel at or near the bottom.
  • Raw material is supplied via a pipe 14, combustion air through a pipe 9 from a cooler 7 which is coupled after the second reactor 5, and which in the example shown is a cyclone cooler, while solid, flowing or gaseous fuel is supplied via a burner 8.
  • the reactor 5 is a fluid-bed reactor with a material supply 15, a fuel supply 8, a material outlet 16 and a fan 6 for blowing in air through a pipe 11.
  • Particulate raw material is fed to the plant at an inlet 1 and is preheated in a pipe 13 and a cyclone 2 by calciner exit gases supplied via a pipe system 17.
  • a fan 10 draws the air/gas stream through the plant.
  • the finished calcined product is discharged from the plant at an outlet 12.
  • the preheated and dried raw material, carbonate-apatite raw phosphate is fed to the first reactor 3 to be heated therein to a calcining temperature of 700°-850° C., at which the majority of the organic components contained in the raw material are burnt away.
  • the retention time of the material in the first reactor is relatively short and limited to 1.5-4 seconds.
  • the reactor 3 operates with a low oxygen percentage of 0-3, and therefore with a limited air surplus, which is regulated by means of the fan 10.
  • the hot material containing a residual amount of organic components and a smaller amount of sulphide formed in the first stage is passed via a separator 4 to the fluid-bed reactor 5 having a relatively long material retention time of at least four times the material retention time in the first reactor 3.
  • the reactor 5 operates with a high oxygen percentage, which in practice is at least twice as high as the oxygen percentage in the reactor 3, and in a similar temperature range of 700°- 850° C.
  • the high oxygen percentage is achieved as the majority of the organic material is already burnt out, and because the treated material at its introduction into the reactor 5 already has a high temperature, resulting in a low oxygen consumption for combustion of fuel in that reactor.
  • the high oxygen percentage ensures optimum removal of the residual amount of organic components and sulphide.
  • From the reactor 5 the material is passed to the cooler 7, prior to being discharged as calcined product at the outlet 12.
  • the spent, hot cooler air is reused as combustion air in the reactor 3.
  • the optimum reaction temperature for the process must thus be sought in the range 700°-850° C., the lowest temperature being chosen for geologically young raw phosphates, and the highest for old raw phosphates. Furthermore, it has been found that this optimum temperature serves to retain a suitable residual CO 2 content in the carbonate-apatite, by which is ensured a suitable reactivity in the "attack"-tank used for the phosphoric acid production. In addition the CO 2 developed by contact with the acid can contribute towards a desired cooling during the acid production.
  • the following experimental data are examples of what can be achieved by two stage calcining as compared with one-stage calcining:
  • the raw material isixie Youssoufia-phosphate which further has a moisture content of 15-18%, which must be dried away before calcination is initiated.
  • By one-stage treatment in flash it is possible, at approximately 750° C., to achieve a product which is fairly acceptable as to sulphide, but the carbon and CO 2 content are high. Attempts to decompose the latter by raising the temperature to e.g. 900° C. will cause the sulphide content to grow to a quite unacceptable level, whereas the BET-value decreases strongly.
  • By one-stage calcining in fluid-bed with retention time 20 min. at 750° C. is achieved an acceptable product, but by a process having an extremely high power consumption. Only by two-stage treatment according to the invention are simultaneously achieved acceptable combinations of low carbon, CO 2 and extremely low sulphide values.
  • the power consumption by the method according to the invention is less than half the power consumption by the above fluid-bed.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
  • Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
US06/652,329 1983-09-28 1984-09-19 Method and apparatus for burning away organic components in raw phosphate Expired - Lifetime US4605370A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DK443383A DK443383A (da) 1983-09-28 1983-09-28 Fremgangsmaade og apparat til bortbraending af organiske bestanddele i raafosfat
DK4433/83 1983-09-28

Publications (1)

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US4605370A true US4605370A (en) 1986-08-12

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US06/652,329 Expired - Lifetime US4605370A (en) 1983-09-28 1984-09-19 Method and apparatus for burning away organic components in raw phosphate

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US (1) US4605370A (da)
DE (1) DE3434237A1 (da)
DK (1) DK443383A (da)
FR (1) FR2552417B1 (da)
MA (1) MA20237A1 (da)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4026272A1 (de) * 1990-08-20 1992-02-27 Kurt Kugler Verfahren und einrichtung zur thermischen behandlung von stoffen nach dem wirbelschichtverfahren
WO2018002793A1 (en) 2016-06-27 2018-01-04 Flsmidth A/S Apparatus and method for removing cadmium from a calcined material

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2670193A (en) * 1949-05-09 1954-02-23 Kellogg M W Co Controlling flow of fluidized solids
US3995987A (en) * 1975-03-31 1976-12-07 Macaskill Donald Heat treatment of particulate materials
US4025295A (en) * 1974-06-18 1977-05-24 F. L. Smidth & Co. Method of burning pulverous raw material and rotary kiln plant therefor
US4504319A (en) * 1982-12-04 1985-03-12 Klockner-Humboldt-Deutz Ag Method and apparatus for burning cement clinker
US4514170A (en) * 1982-10-12 1985-04-30 Krupp Polysius Ag Apparatus for the heat treatment of fine-grained material

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2486924A1 (fr) * 1980-07-17 1982-01-22 Anvar Procede d'enrichissement des minerais de phosphates indures a exogangue carbonatee et installation pour la mise en oeuvre de ce procede
US4389380A (en) * 1982-01-12 1983-06-21 Agrico Chemical Company Multiple-stage thermal beneficiation process for phosphate ores
DK157442C (da) * 1982-12-07 1990-06-05 Smidth & Co As F L Fremgangsmaade og apparat til kalcinering af fosfat

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2670193A (en) * 1949-05-09 1954-02-23 Kellogg M W Co Controlling flow of fluidized solids
US4025295A (en) * 1974-06-18 1977-05-24 F. L. Smidth & Co. Method of burning pulverous raw material and rotary kiln plant therefor
US3995987A (en) * 1975-03-31 1976-12-07 Macaskill Donald Heat treatment of particulate materials
US4514170A (en) * 1982-10-12 1985-04-30 Krupp Polysius Ag Apparatus for the heat treatment of fine-grained material
US4504319A (en) * 1982-12-04 1985-03-12 Klockner-Humboldt-Deutz Ag Method and apparatus for burning cement clinker

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4026272A1 (de) * 1990-08-20 1992-02-27 Kurt Kugler Verfahren und einrichtung zur thermischen behandlung von stoffen nach dem wirbelschichtverfahren
WO2018002793A1 (en) 2016-06-27 2018-01-04 Flsmidth A/S Apparatus and method for removing cadmium from a calcined material

Also Published As

Publication number Publication date
FR2552417B1 (fr) 1988-07-08
DK443383A (da) 1985-03-29
FR2552417A1 (fr) 1985-03-29
DE3434237A1 (de) 1985-04-11
MA20237A1 (fr) 1985-04-01
DK443383D0 (da) 1983-09-28

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